Studer RHU 450 from the 1960s

I've found it useful to have a surface grinder, and have been thinking about geting a cylindrical grinder. Well, one came along that appeared to be in such good shape that I made an impulse purchase. As with my J&S 540 surface grinder, I never saw it in person, just talked with the seller on the phone, and thought it was a good risk.

The machine is a Studer RHU 450 from the mid-1960s. The centers are 100 mm (4 inches) above the table and the left/right travel is 450mm (18 inches). The work head can be rotated up to 90 degrees, the wheel head can also be rotated 90 degrees, and has both a cross slide and an angled slide. The table can be rotated +- 10 degrees and locked. The wheel head has a 300mm (12") wheel on the left side and has a smaller taper on the right that take a 200mm (8") wheel.

The work head has a variable-speed DC drive motor which can go from about 10 rpm to 650.

The machine was manufactured in Switzerland, and that's also where I bought it from. The nameplate has been removed, but I found the number 587 stamped on table and on the work head, so I'm pretty sure that's the machine number.

It was delivered yesterday, and I spent most of the day today going through the maintenance schedule, learning how the controls work (obscure!!) and trying to see if there were any "gotchas" in the deal. The machine came with 200 pages of German-language documentation, and I've also gotten a copy of the English language manual (50 pages shorter).

The paint matches inside and outside, so I believe that either it's original or the machine has been completely refurbished. The only thing I have found so far that doesn't work is that the handwheel for the long axis (on the left in the photo) is supposed to have two modes, 25mm per revolution and 2mm per revolution. The 2mm per rev doesn't engage. I suspect that the planetary gears inside are gummed up. I'll take it apart and free it up.

The hydraulics feels a bit 'soft', for example when I slow down to a crawl, it sometimes comes to a complete halt, pauses for a second or two, then resumes. I suspect that there is still air in the hydralics.

The bottom side of the slides still has a nice set of scraping marks, as well as a couple of deep scratches. I put a 1 micron/division indicator (0.00004"/division) on the wheelhead and ran along both axes of the table the full travel. The indicator didn't budge. There is no wear under the tailstock or in the tailstock barrel, again a good sign.

Both the work head and the wheel head have plain bearings. The first calls for Mobile Velocite 6 and the second for Mobile Velocite 3. The work head bearing is spring-loaded, and I adjusted the end play as per the manual. It seems to have a 10:1 internal taper, because the 0-10 micron range play correponds to 1-100 microns of axial float. A two micron indicator inside the MT5 taper shows no deflection when rotating.

I was going to also adjust the wheel head bearings, which at first I thought felt a bit tight. But I have never had a machine with plain bearings before (my mill, lathe and surface grinder all have greased ball and needle bearings) so decided just to try it. (My late father's voice, saying "if it ain't broke, don't fix it" was also echoing in my head.)

I ran the wheel head for just a few seconds, then for a couple of minutes, then for longer. It gets warm to the touch, but not hot. I had an "oh shit" moment when at first a bunch of oil got flung out, but that stopped and the oil level stayed OK, so I think that might have been oil that got sloshed around into the wrong place during transport.

The machine can accomodate W25 collets in the work head, but came with an almost-complete set of W20 1-20mm Schaublin collets along with an MT5 holder, a regular drawbar, and a "quick-open" drawbar. There are also a bunch of dead centers for the work head and tailstock. I have a very complete set of metric and inch 5C collets, so I might buy a 5C to MT5 taper adaptor and modify one of the drawbars to hold the 5C collets from the inside. (The spindle is about 30mm = 1.2" ID).

The downside was that the machine came without either a fixed or traveling steady, without a work head chuck, with 2 extra wheel flanges that are the wrong size, with a balancing mandrel that's the wrong size, and without an internal grinding spindle or extra pulleys for changing the wheel speeds. So I'll have to watch for these to pop up used or make my own.

If anyone out there has one of these machines and can help me to figure out some things, I'd be grateful. For example there seems to be an automatic stop system which I have not understood. This microswitch is "parked" on the end, but obviously is meant to be fixed where the table can contact it.

Very nice machine!
I have been looking for something like that in my price bracket for a long time, but without success.
The best OD grinder I have is a Myford MG12ME with ID spindle, but this has no auto in-feed and is kind of small. Getting the accessories together has taken me years and I am still missing stuff.
I have been looking at Studer, Kellenberger and Tschudin, but a complete one with all the fixings is either rare, far away, or too expensive and I do not understand their naming convention.
Which have auto in-feed, sparkout, auto-retract/auto-cycle? With Myford that would be the HPT or HPM model (I think).
I recently looked at at Ziersch & Baltrusch in as new condition, but could not agree on a price. That thing was like new and with all the fixings. Afterwards it turned out to be an outsourced model made in Hungry with questionable quality.
So I am yealous of you score. Does Studer still carry parts for those models?

Bruce, I'm curious what size the extra wheel hubs you have are.
My Studer Type 1 is missing the smaller right side wheel hub.
The arbor is about 22mm long with the big end being about 22mm and the small end 15mm.

That is a very clean machine! (BTW I thought you were also on the hunt for a lathe, did you found one?)
I do not very much cilindrical grinding but still I do own several machines as odd or broken machines are chaep.Learned that the only brands that counts in this field are Kellenberger and Studer.
Note that the MT5 on your Studer is different from a regular one.

Martin, the Myford MG12 was one of the grinders that I would have gotten if one had turned up in good condition. I have read a lot of good things about them. Regarding parts, the people at Studer have been very helpful. Before the machine arrived, they sent me manuals in German and English, and also gave me some information about transporting the machine. But I have not yet asked for part prices. The manual lists prices from the 1960s, and they already seem very steep. So if I add in fifty years of inflation, they will be unaffordable. But I'll ask anyway, just to be sure.

Rusty, here is a picture of the two hubs that I received, which don't fit my machine. They are for wheels with a 76mm ID, maximum width 25mm. The OD of the flanges is 130mm, and the puller thread is M40 x 1.5mm right handed. The nut which secures the flanges on the hub are M65x2mm left hand. The taper section has a length of about 48mm and tapers from 29.8mm to 25.0 mm in diameter. (Note that this is 4.8mm in 48mm, so a 1:10 taper.) I don't think that these hubs will fit your machine, but am hoping that someone here can identify them. I will try and trade these for hubs that fit my RHU 450.

Today I spent some time to check the geometry of the machine more carefully. The most important part of the geometry for accuracy is the straightness of the travel. I checked this first against the side of the table and secondly on a test bar. Both are good to a micron (40 millionths of an inch):

(second video below)

Along the vertical axis the machine is less accurate. The table rises about 8 microns over 450mm (which might be dirt or corrosion under the rotating table)

(third video below)

But the tailstock is about 60 microns (0.0025"!) higher than the work head. I am going to study this more carefully, as the only explanation that would make sense is that the tailstock comes from a different machine. It's also shifted towards the front by about 30 microns compared to the work head, but that matters very little because in practice one rotates the top table to make the line of centers parallel to the travel. Fortunately neither of these offsets will have much effect on accuracy, and I could regrind the tailstock base to remove both of these errors, then scrape in some oil pockets. (Richard, if you see this message, please comment if you think that would make sense. The alternatives would be to shim the work head or simply to live with it.)

(fourth video below)

I ran the wheel head for successively longer periods. The last run was for nearly two hours. The spindle housing got pleasantly warm to the touch (34 Celsius, 93 Farenheit), and runs smoothly and without vibration.

Something that I will be needing is a 40mm diameter dial indicator with micron divisions, that goes here.

Finally, I tracked down the source of a worrying noise. The wheel head has a "fast" hydraulic infeed/outfeed function, which can be used for plunge grinding. When I activated this, the wheel head made a squeaking/scraping noise as it moved. I tracked down the cause: the shields on the sides have an internal "wiper" made from spring steel spot welded to the shields. This is damaged on one side and on the other side has some chips and grit inside. So I'll clean these out and if necessary replace them. Should I go with spring steel or use a more modern material?

At this point, I'm starting to gain confidence that this machine was a good purchase. A bit of grinding and scrapring to adjust the tailstock geometry looks like all that is needed. And probably that's not even that important for accuracy.

Whilst thats a nice machine in great condition, just bare in mind currently with out a ID spindle its pretty limited in what it can do. Grinder accessories dont come up as oftern on the bay and when they do if its in good nick it generally gets a good price! Internal spindles are serious coin new, that said now you have a OD grinder making your own spindles aint as impossible as it use to be!

Equally take care with that wheel, blowing a wheel on a J&S 540 is unlikely to be fatal, that is far bigger and your naturally a lot more in front of it!

Equally take care with that wheel, blowing a wheel on a J&S 540 is unlikely to be fatal, that is far bigger and your naturally a lot more in front of it!

Yes, understood. It makes me nervous just standing in line with the wheel on my bench grinder, and this is a lot more serious. I plan to only grind air for some time until I am very familiar with the controls. Based on other things I have read here, I've also ordered a copy of Vol 2 of Machine Shop Practice by K. H. Moltrecht to study.

I would be grateful for tips here about things to avoid and practices that will improve safety.

The tailstock center is spring loaded. Does that mean that if there is a crash it is more likely to throw the work than to break the wheel?

Regarding the missing internal spindle, I figure that if I can't find one, I might be able to repurpose a lathe support grinder.

Yes, understood. It makes me nervous just standing in line with the wheel on my bench grinder, and this is a lot more serious. I plan to only grind air for some time until I am very familiar with the controls. Based on other things I have read here, I've also ordered a copy of Vol 2 of Machine Shop Practice by K. H. Moltrecht to study.

I would be grateful for tips here about things to avoid and practices that will improve safety.

The tailstock center is spring loaded. Does that mean that if there is a crash it is more likely to throw the work than to break the wheel?

Regarding the missing internal spindle, I figure that if I can't find one, I might be able to repurpose a lathe support grinder.

Cheers,
Bruce

Having a spring loaded tailstock center means you get to eat 'em both. Seriously it's purpose is to apply a consistent pressure on the work piece to avoid distortion. Lack of a steady or follower on a machine this short is not likely a problem. If necessary I have seen a follower cobbled from a piece of close grained oak wood that worked quite well. You are smart not to jump in there and take chances on a grinding machine that you are not familiar with. Grinding air is good. If possible find someone with experience on that or a similar machine to make the first sparks. Grinding is fun. Hell, how can a machinist not have fun routinely hitting tenths or even millionths? Wheel and work in your face? Not so much.

Pretty sure the tailstock is spring loaded to provide constant tension on the workpiece and allow for thermal expansion, not as a safety feature.
Guess it depends on what you have in mind making/modifying but a guy around here could do lots with an OD grinder and no ID spindle.
Looks like a very nice machine, congratulations.

That’s a nice machine for sure.
One safety measure i allways take is without a workpiece first check if the fast retract of the spindle isnt in the rear position.

I allready made a mistake once and thought to retract, but the head came forward. My handle does not say which way is what.
That was the first time running the machine. I am not making that mistake again.

^ Thats pretty common with most Morse tapers in any kinda rotating head, there almost always std just short and done such that the work - tool hangs out a little more. Grinding is a pretty low force job hence a bit of stick out realy is not the issue it is on a lathe.

Tailstocks on grinders from new are oftern a nats high, like that as they wear they become more accurate before being less accurate. Equally you need to seriously question just how much of that is indicator droop, gravity effects everything and at these levels of measurement it can be suprising!

It's just shorter than normal, correct? I've already checked it's length, and an 5C-MT5 collet holder will fit OK. So I can make an internal drawbar and use my 5C collet set.

I thought is was a bit smaller in diameter. I was told that was done to prevent people might use random MT5 tooling used by others in the shop and damaging the taper.
I do have a Studer RHU 500 in a very sorry condition with some accessories. Had the idea of making running it again, but now I have 2 Kellenbergers complete with almost all accessories so I don't think I will ever gonna use the Studer.

Tailstocks on grinders from new are often a gnats high, like that as they wear they become more accurate before being less accurate. Equally you need to seriously question just how much of that is indicator droop, gravity effects everything and at these levels of measurement it can be surprising

Gnats high would be 5 microns (0.0002"). This is 50 microns (0.002")! None of this is indicator droop, I double checked this by running the tailstock up to the work head and putting a centricator in the workhead.

Maybe if the tailstock was sliding back and forth every five minutes for a decade on a dirty table, it would wear that much. But it's not going to happen on my machine, so if I can confirm this, I am very tempted to surface grind the tailstock base to bring it into alignment. The alternative would be to shim the work head. I happen to have some 0.002" shim stock, but this approach doesn't seem like the right thing for such a classy machine.

I was told by a rebuilder of Jones & Shipmans that they aim for 0.0005" high for the tailstock.

That's 12 or 13 microns, still a lot compared to the accuracy in the horizontal direction, which is a micron. Frankly I don't get it. I'm hoping that Richard King will show up here and explain this better.

(If the reason for doing this was to allow for wear, that doesn't make sense to me. After all if the tailstock base is worn and the tailstock is low, you can just grind or scrape the base of the work head to compensate. The ways are flat and parallel, so grinding the work head base to lower it to a worn tailstock is an easy job on a surface grinder. On my machine the work head base sits on a rotary plate, so it would be enough to remove the rotary plate, put it on the surface grinder, and take off enough to lower the work head to match the tailstock.)

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